2 things.... the bed extender will NOT lock in the insode position but doesent make noise or rattle and it coveres the storage compartments.... you can access with removal or with folding the corners..
In our area (Tulsa) there are stores called "Tractor Supply" where I bought a 1/2 " thick 4' x 6' recycled rubber stall matte for $20 bucks. You can trim the end and make lay -in pieces for the sides at front and back. Works good as you can remove back ones to access bed boxes. Also you can cut holes into it so your bed extender will sit on the bed.